Conjugacy, orbit equivalence and classification of measure preserving group actions

We prove that if G is a countable discrete group with property (T) over an infinite subgroup H < G which contains an infinite Abelian subgroup or is normal, then G has continuum many orbit inequivalent measure preserving a.e. free ergodic actions on a standard Borel probability space. Further, we obtain that the measure preserving a.e. free ergodic actions of such a G cannot be classified up to orbit equivalence be a reasonable assignment of countable structures as complete invariants. We also obtain a strengthening and a new proof of a nonclassification result of Foreman and Weiss for conjugacy of measure preserving ergodic, a.e. free actions of discrete countable groups.